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MARTIN METGALF, OF GRAND RAPIDS, MICHIGAN.

Letters- Patent No. 81,809, dated September I, 1868.

IMPROVEMENT IN HOT-AIR I'UBLNAGBS.

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Bc it known that I, 'MARTIN METCALF, of Grand Rapids, in thc countyof Kent, and in the State of Michigan, have invented certain new and useful Improvements in Hot-Air Furnaces; and I do hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings, and the letters of reference marked thereon.

In the annexed drawings, making a part of this specification#- Figure lrepresents a. cross-section, and Y Figure 42 represents a longitudinal section of my furnace.

A represents the outer brick or metallic case, provided with suitable doors hinged thereto, leading into the tire-box C, and to the drum D, Vwhich is situated immediately above the fire-box. The case A is also .provided with slots or passages zr, at suitable distanceslapart alongits bottom or lower edge, for the purpose of allowing or conducting the cold air of the room to the heating-surface ofthe fire-box and drum.

B represents another box, of smaller dimensions, corresponding in shape to the outer case A, andprovided with slots x, also corresponding with the slots through the outside ofthe furnace, and provided with a. projecting horizontal edge or ange,f,just so as to t inside ot' the outer case A nearly equidistant from the top and bottom ofthe same. The flange or partitionfhas a suitable number of small holes, to allow the passage of air from the chamber below said partition to the one above thesame, and vice versa.

. Near the'bottom of the inner box B is adjusteda rebox, G, ot' such shape and dimensions asmay be required, which isprovded with a suitable door to close the same when it becomes necessary so to do, and directly above the `said ire-bo is adjusted a drum, D, which has a cylindrical pipe, D,vruuning through its centre longitudinally. v The ends of the drum D, between its edge and 'the edge ofthe pipe D', are closed, thereby forming an air-chamber between the sides of the said pipe and drum. The inner pipe D projects beyond the drum Dand downward, so that the passage-thronghsaid pipe `is extended and conducts the air from the chamber between. thc boxes A and B, below the partition f, through said pipe forward, and thence into the chamber above the drum D. y f

A connecting smoke-pipe, e, conducts the smoke from the rear end of the'rc-box into the chamber of the drum D,and thence it passes forward, and is carried ollby means of a smoke-pipe, E, attached to the front end ofthe drum D, and ertcnding up through the top of' theboxes B and A ofthe furnace.

A series of pipes, R, is secured in the vdrum D, and, extending downward, is adjusted or fastened in the sides of the boxiB, below the horizontalpartitionf, and corresponding pipes S are placed `within the drum D, and extend upward, making a series of cylindrical pipes extending through the drum D, from the-bottom to the top thercot`. v t

F represents a'covervfor the outside box A, with a metallic radiator, ot' such shape and dimensions as may be most suitable, and represents a chimney surrounding orv in lieu of the smoke-pipe E, and extending as high as'reqnired.

G represents a pipe leading from the chamber above.the drum D, into which the hot air, from all sources, is first conducted, and thence through the pipe G to any place desired.V

II represents a small pipe or hole leading from the back side of the furnace into the lire-box C, which may i i be closed by means of a. cut-o` valve orbutton secured on the outside of the furnace.

I tl will be seen that the cold air from the outside of the furnacepa'sses through' the passages x and upward I through the pipes R, and is brought directlyL in contact with the hot surface of the drum D, and passes thence into the chamber above said drum, and is conducted wherever it may be desired by means of' the pipe G. A

part ofthe cold air from the outside may pass through-the passages m and corresponding slots a: of the inner box B, and come directly in contact with the' heated surface of there-box C, and passes thence around the outside of the heated druruD into thechamber above, and thence'as' above described. n

Thus it is obvious that the ,coldest air from the outside is conducted directly to the hottest surfaces inside of the furnace, and therefore more heatiis imparted to the air than by any other known device.

Having thus fully described my invention, what I claim as new, und desire to secure by Letters Patent, is

1. The pipes R, or their equivalents, when arranged with a drum, D, and extending downward as described, and for the purpose specified. I

2. The combination of a ease, A, provided with passages x and a) box, B, provided with a. projecting ange, f, and slots with the pipes R and the drum D, when constructed and arranged substantially es and for the purpose herein set forth.

In testimony that I claim the foregoing, I have hereunto set my hand, this 11th day of December, 1867.

`MARTIN METCALF.

Witnesses: o

T. SINcLAIn,

H. L. -OR1TTENDEN. 

